A direction indicator system of a vehicle (motorbike, car and the like) includes right and left direction indicator lamps, an ignition switch, a direction indicator switch, a hazard switch, a battery, and a direction indicator device. Of these, the direction indicator device operates with a voltage supplied from a battery to control lighting of the direction indicator lamps depending on a state of the direction indicator switch or hazard switch. For example, the direction indicator device performs a hazard operation to blink both the direction indicator lamp on the left side and the direction indicator lamp on the right side, in a case where the ignition switch is in an ON state when the hazard switch is turned on.
Moreover, the direction indicator device has a hazard maintaining function for maintaining a hazard operation until the hazard switch is turned off even if the ignition switch is turned off during the hazard operation. This hazard maintaining function has been attained using a microcomputer, a logic circuit or the like in the related art.
For example, Patent Literature 1 attains the hazard maintaining function using a current detecting circuit, a maintaining circuit and a blink controlling circuit. The maintaining circuit determines whether or not the hazard operation is in operation on the basis of a current flowing in each direction indicator lamp detected by the current detecting circuit. The blink controlling circuit controls maintaining of a blinking signal on the basis of a determination result by the maintaining circuit. In other words, in a case where the maintaining circuit determines that the hazard operation is in operation, the blink controlling circuit maintains the current for blinking the direction indicator lamps even after the ignition switch is turned off.